Cell site power system management, including battery circuit management

ABSTRACT

Systems, apparatuses, and methods for managing battery circuits in systems such as wireless communications service base stations are disclosed. An example apparatus includes a battery circuit having multiple strings of one or more serially connected batteries. The apparatus may be configured to rotate between battery strings such that one or more strings are maintained at or near an upper threshold while other string(s) are disconnected from the maintained string(s). The apparatus may also be configured to charge the battery circuit, to test the battery circuit, and to handle power failures.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/726,265, filed on Mar. 17, 2010, and entitled“CELL SITE POWER SYSTEM MANAGEMENT, INCLUDING BATTERY CIRCUITMANAGEMENT,” which is hereby incorporated herein in its entirety byreference. This application is also related to International PatentApplication No. PCT/US2010/043263 filed Jul. 26, 2010, which isincorporated by reference herein in its entirety.

BACKGROUND

The popularity of commercial wireless communications services (e.g.,wireless telephony, wireless network access, and wireless email) hassubstantially increased during recent years. In many cases, users, suchas consumers, mobile workers, emergency response personnel, and thelike, now utilize these services for both personal and businesscommunications. Likewise, users are also increasingly relying on theseservices. For example, some households forgo wired telephone service infavor of wireless telephone service, some government agencies rely onthese services for both routine and emergency communications, andbusinesses rely on these services to communicate with customers andmobile workers. Correspondingly, the cost (both financial andnonfinancial) of outages is also increasing.

Typical commercial wireless communications service (CMRS) providers relyon remote facilities to provide services, such as base stations (e.g.,cell sites, radio repeaters, wireless to backhaul interfaces, etc.). Ifa base station experiences a loss of externally provided electricalpower (e.g., due to natural disasters, rolling brownouts, accidents,etc.), users near the base station may experience a service outage. Todecrease reliance on externally provided power, many base stationsinclude backup batteries. However, the amount of energy storable inbackup batteries of a base station is typically limited by constraintssuch as maximum size, weight, and cost, etc.

Recent advancements in battery technology have drastically increased theamount of energy that can be stored (e.g., the amount of energy per unitsize, per unit weight, etc.). Further, recent advancements have alsodrastically increased the rate at which batteries may be charged and/ordischarged and improved the self-discharge rates. In light of these andother advancements, it may be beneficial to more effectively managebattery circuits, for example, to increase the amount of time that basestations can operate from battery circuits, to increase battery circuitlongevity, to detect battery circuit failures, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an environment for practicing theinvention;

FIG. 2 is a block diagram of a suitable base station for use in theenvironment of FIG. 1;

FIG. 3 is a block diagram of a suitable power controller usable in thebase station of FIG. 2;

FIG. 4 is a schematic diagram of a suitable battery circuit usable inthe base station of FIG. 2;

FIG. 5 is a logical flow diagram of a suitable process for managing abattery circuit;

FIG. 6 is a logical flow diagram of a suitable process for chargingand/or testing a battery circuit; and

FIG. 7 is a logical flow diagram of a suitable process for handling apower failure.

DETAILED DESCRIPTION

The following description provides specific details for a thoroughunderstanding of, and enabling description for, various embodiments ofthe technology. One skilled in the art will understand that thetechnology may be practiced without many of these details. In someinstances, well-known structures and functions have not been shown ordescribed in detail to avoid unnecessarily obscuring the description ofthe embodiments of the technology. The terminology used in the belowdescription should be interpreted in its broadest reasonable manner,even though it is being used in conjunction with a detailed descriptionof certain embodiments of the technology. Although certain terms may beemphasized below, any terminology intended to be interpreted in anyrestricted manner will be overtly and specifically defined as such inthis Detailed Description section.

When a power outage occurs, often it is in the context of a crisissituation (e.g., storm, natural disaster, etc.) where emergency servicepersonnel and others may rely even more heavily on mobiletelecommunication services. Base stations, including those nearhospitals, police and fire stations, etc., may therefore utilize abackup battery circuit to avert service interruptions during a poweroutage. A typical base station constantly maintains all the batteries inits battery circuit in a fully charged state using a continuous chargingsource, with the ostensible goal of ensuring that the base station canoperate for the longest possible time during a power outage.

The applicants recognized certain drawbacks of this approach. As oneexample, constantly charging batteries causes chemical erosion and otherdetrimental effects that reduce the lifetime of the batteries. A reducedbattery life may mean that backup battery circuits are more likely tofail during a critical period. Reduced battery life can also be costly:a telecommunications provider with a widespread access network may spendupwards of $10 million a year on replacement batteries, for example.Reduced battery life can also have significant environmental impacts,since often times base stations utilize lead-acid or similar batteriesthat may generate pollutants during charging and/or require specialdisposal. Due to the environmental impact, governments may levy taxesand fees against the operator of a base station on a per-battery basisand/or require special operational protocols (e.g., obtaining anofficial “death certificate” that verifies that an operator properlydisposed of a dead battery). These regulations may further increase theoperating expenses of base stations in proportion to the number ofbatteries consumed.

Applicants have realized that the goal of maximizing backup time duringa power outage must be balanced against the goal of improving thelifetime of batteries. Given the recent advances in battery technology,some batteries have self-discharge rates as low as approximately 2-3%per month and may be smaller and/or less expensive than before. Theseadvances mean that a base station may “park” extra batteries by givingthem a break (e.g., a month-long break) from constant charging, whichimproves their lifetimes. The length of the break will depend in part onthe self-discharge rate. A base station may then only charge the parkedbatteries intermittently (e.g., monthly) in order to maintain them at anacceptably high level of charge (e.g., 95%) at all times. To furtherimprove battery lifetimes, a base station may rotate the variousbatteries so that each spends an approximately equal amount of time in aparked state. During a power outage, the base station may, with propermanagement, utilize both the fully charged “active” batteries and thepartially charged “parked” batteries to provide power to the basestation.

Constantly charging all batteries also makes it more difficult to test abattery for failures. Testing a fully charged battery for failurestypically requires that the base station first actively discharge thebattery, which further reduces that battery's lifetime. Since a parkedbattery naturally self-discharges while it is parked, a base station maytest the parked battery for anomalies or failures during theintermittent charging of the parked battery, without first activelyforcing a discharge of the battery. To test a battery for anomalies, thebase station may compare the battery's charging behavior against thecharging behavior of other batteries and/or against expected/empiricaldischarge rates. In this way, parking batteries improves the lifetime ofthe batteries while still providing regular testing of the batterycircuit.

Systems, apparatuses, and methods for managing battery circuits insystems such as wireless communications service base stations aredisclosed. An example apparatus includes a battery circuit havingmultiple strings of one or more serially connected batteries. Theapparatus may be configured to rotate between battery strings such thatone or more “active” strings are maintained regularly or continuouslywith a charging float voltage source or other type of maintenance sourcewhile one or more other “parked” strings are disconnected from themaintained active string(s) and the charging float voltage source. Theapparatus may also be configured to charge the battery circuit, to testthe battery circuit, to rotate battery strings, to handle powerfailures, etc.

An example process provides a method for charging and/or testingmultiple battery strings. The process may select a parked string,connect it to active string(s) and a charging source, charge and testthe selected parked string, and disconnect the selected parked string.The system may then provide a top-off charge to all of the batterystrings in parallel.

Another example process provides a method for handling a power failureusing multiple battery strings. The process may monitor the voltage ofconnected string(s) that discharge while those strings provide power toa load during a power failure. As the voltage of the connected string(s)drops due to the power demands of the load and eventually reaches thevoltage of a parked string, the system may select the intercepted parkedstring and connect it to the load.

Utilizing and rotating between multiple battery strings results inseveral benefits. First, the system reduces unnecessary charging,resulting in lower power expenditures and less heat in the batterycompartment. Second, each string may spend less time on a float voltagesource, so the average battery life may increase, and batteries are lesslikely to become unbalanced. Third, the system may test batterieswithout discharging the batteries, which also improves the average lifeof the batteries. Fourth, the system may remotely test the variousbattery strings and send alerts as strings fail, reducing the need forservice calls. Fifth, if necessary, the combined charge of the variousstrings provides increased battery capacity to increase the system's runtime during a power failure. Other benefits of course exist.

Suitable System

FIG. 1 is a block diagram of environment 190 in which the invention maybe practiced. As shown, environment 190 includes base station 100configured to wirelessly communicate with wireless devices 197-199. Basestation 100 includes antenna 192, is coupled to back-haul 194, and isconfigured to receive power via primary power signal PRI_IN andalternate power signal ALT_IN.

Base station 100 may include virtually any device for facilitatingwireless network access. For example, base station 100 may be a wirelesstelephony base station, a wireless network access base station, awireless email base station, and/or the like. In one embodiment, basestation 100 is operated by a mobile telephony service provider or CMRS.Generally, base station 100 is configured to provide a network interfacefor wireless devices 197-199 by providing an interface (via antenna 192)between wireless devices 197-199 and back-haul 194. Base station 100 andwireless devices 197-199 may communicate using any wireless protocol orstandard. These include, for example, Global System for MobileCommunications (GSM), Time Division Multiple Access (TDMA), CodeDivision Multiple Access (CDMA), Orthogonal Frequency Division MultipleAccess (OFDM), General Packet Radio Service (GPRS), Enhanced Data GSMEnvironment (EDGE), Advanced Mobile Phone System (AMPS), WorldwideInteroperability for Microwave Access (WiMAX), Universal MobileTelecommunications System (UMTS), Evolution-Data Optimized (EVDO), LongTerm Evolution (LTE), Ultra Mobile Broadband (UMB), and the like.

Back-haul 194 may be any connection that provides a network interfacefor base station 100. For example, back-haul 194 may include one or moreT-1 connections, T-3 connections, OC-3 connections, frame relayconnections, Asynchronous Transfer Mode (ATM) connections, microwaveconnections, Ethernet connections, and/or the like. In addition,back-haul 194 may provide an interface to a telephone switch (e.g., to a5ESS switch or a Private Branch Exchange switch), to a data network(e.g., to a router or network switch), and the like.

Base station 100 may also be configured to receive power via primarypower signal PRI_IN, for example, as alternating current (AC) power froma public utility, from a power grid, from photovoltaic power sources(e.g., solar panels or arrays), from a turbine, from a fuel cell, from agenerator, and/or the like. However, primary power signal PRI_IN may beprovided by virtually any power source and may be provided as either ACand/or direct current (DC) power.

Further, base station 100 may also be configured to receive power viaalternate power signal ALT_IN, for example, an alternate energy powersource. Alternative energy sources may include photovoltaic powersources, wind power sources, geothermal power sources, generators, fuelcells, bioreactors, and/or the like. In typical environments, DC poweris received by base station 100 via alternate power signal ALT_IN.However, either AC and/or DC power may be received via alternate powersignal ALT_IN.

At times, however, primary power signal PRI_IN and/or alternate powersignal ALT_IN may provide insufficient power to operate base station100. Accordingly, base station 100 may also include a battery circuit,as discussed below.

Wireless devices 197-199 may include virtually any devices forcommunicating over a wireless network. For example, wireless devices197-199 may include mobile telephones (e.g., cellular telephones, GSMtelephones, TDMA telephones, LTE telephones, etc.), wireless datadevices (e.g., Personal Digital Assistants (PDAs), computers, pagers,etc.), and/or the like.

One skilled in the art will appreciate that although illustrated in thecontext of a wireless telecommunications environment, the invention maybe practiced in any environment in which backup power serves acommercial, public, or private operation or system reliant uponelectrical power.

FIG. 2 is a block diagram of a portion of base station 200. Base station200 includes power controller 210, rectifier and switch circuit 230,primary power interface 240, alternate power interface 250, batterycircuit 260, alternate power source 290, and communications interface280. Base station 200 may be employed as an embodiment of base station100 of FIG. 1.

In some examples, base station 200 includes an alternate power source290 that is configured to provide power via alternate power signalALT_IN and may include any of the example alternate energy power sourcesdescribed previously with respect to FIG. 1. For example, alternatepower source 290 may comprise photovoltaic power sources (e.g., solarpanels or arrays) arranged on the exterior of base station 200.

Power controller 210 is configured to control the power systems of basestation 200. As illustrated, power controller 210 is configured toreceive or provide control signals 212, to receive status signalsCOM_STAT, RECT_STAT, and STR_SNS, and to provide output/control signalsRECT_CTL, ALT_CTL, STR_EN, and STATUS, as discussed below.

Power controller 210 is also configured to manage and control theoperation of rectifier and switch circuit 230 and battery circuit 260based, at least in part, on the various status and control signalinputs. For example, when a primary power signal is available to thesystem, power controller may utilize control signals RECT_CTL and STR_ENto coordinate the charging and/or testing of battery circuit 260. When aprimary power signal PRI_IN and/or alternate power signal ALT_IN fails(e.g., during an external power outage), power controller may utilizecontrol signals RECT_CTL and STR_EN to route battery power from batterycircuit to communications interface 280 and/or power controller. Theoperation of power controller 210 is discussed in further detail withregards to FIG. 3.

Rectifier and switch circuit 230 is configured to selectively routepower between and/or among primary power interface 240, alternate powerinterface 250, battery circuit 260, communications interface 280, andpower controller 210. For example, rectifier and switch circuit 230 maybe configured to selectively power communications interface 280 from oneof primary power interface 240, alternate power interface 250, and/orbattery circuit 260. In addition, rectifier and switch circuit 230 maybe further configured to route operational power to power controller 210(power connection line not shown).

Rectifier and switch circuit 230 may be configured to provide statussignal RECT_STAT to power controller 210 to, for example, indicate thestatus of rectifiers, inverters, chargers, switches, power sourceoutputs, failure conditions (e.g., rectifier failure, inverter failure,switch failure, excessive current draw, out of range inputs/outputs,etc.), and/or the like. Status signal RECT_STAT may be provided to powercontroller 210 to enable power controller 210 to adjust the operation ofrectifier and switch circuit 230 based on these and other conditionssuch as the status of primary power signal PRI_IN, the status ofalternate power signal ALT_IN, and/or the like. Power controller 210 maycontrol the rectification, switching, charging, and other operations ofrectifier and switch circuit 230 via control signal RECT_CTL.

Rectifier and switch circuit 230 may include switching devices of anytype (e.g., field-effect transistors, insulated gate bipolartransistors, junction field-effect transistors, bipolar-junctiontransistors, relays, transmission gates, etc.) that are configured toselectively switch (e.g., route) power among the elements of basestation 200. In addition, rectifier and switch circuit 230 may alsoinclude one or more rectifiers configured to rectify AC power fromprimary power interface 240 and/or from alternate power interface 250 toprovide DC power to communications interface 280, battery circuit 260,and/or power controller 210.

Further, rectifiers, switches, and/or other circuitry of rectifier andswitch circuit 230 may be configured to selectively charge batterycircuit 260 from primary power interface 240 and/or alternate powerinterface 250. For example, rectifier and switch circuit 230 may includeand/or be configured as a trickle charger, a constant current charger, aconstant voltage charger, a constant current/constant voltage charger, adelta-V charger, and/or the like and/or a combination of these.

Primary power interface 240 may be configured to couple primary powersignal PRI_IN to rectifier and switch circuit 230 via power signalPRI_PWR, for example, to power communications interface 280, to chargebattery circuit 260, and/or the like. Primary power interface 240 mayinclude a circuit breaker, line filter, surge protector, power meter,and/or the like. However, in one embodiment, primary power interface 240may simply be a wire segment connecting primary power signal PRI_IN torectifier and switch circuit 230.

Likewise, alternate power interface 250 may be configured to receivepower from an alternate energy source and to couple the received powerto rectifier and switch circuit 230 via power signal ALT_PWR. Forexample, alternate power interface 250 may be configured to receive DCpower from a photovoltaic power source and/or from a generator. As oneexample, alternate power interface 250 may be interfaced to a generatoras discussed in further detail by U.S. patent application Ser. No.12/170,675, entitled “CELL SITE POWER GENERATION,” filed on Jul. 10,2008, which is hereby incorporated by reference. In other examplesthough, alternate power interface 250 may be configured to receive powerfrom virtually any power source, such as those discussed above.

Alternate power interface 250 may include a circuit breaker, linefilter, surge protector, power meter, and/or the like. However,alternate power interface 250 may simply be a wire segment connectingalternate power signal ALT_IN to rectifier and switch circuit 230.Alternate power interface 250 may also be configured to receive controlsignal ALT_CTL, which may be employed, for example, to control analternate power source.

Battery circuit 260 is configured to store power provided by primarypower interface 240 and/or alternate power interface 250 in any numberof batteries or other electrical energy storage devices (e.g.,ultracapacitors, supercapacitors, other capacitors, inductors, etc.),which may be arranged in any combination of series configurations,parallel configurations, and/or series and parallel configurations. Inone embodiment, battery circuit 260 includes multiple strings ofserially connected batteries. As illustrated, battery circuit 260 iscoupled to rectifier and switch circuit 230 via battery power signalBAT_PWR and in some examples, via alternate charging signalALT_CHARGE_PWR. Battery circuit 260 is also coupled to power controller210 via string enable signals STR_EN and string sense signals STR_SNS.Further details regarding battery circuit 260 are discussed inconjunction with FIG. 4, below.

Communications interface 280 is configured to interface wireless devicesto back-haul 294 via antenna 292. Communications interface 280 typicallyincludes both digital and radio frequency (RF) electronics. In oneembodiment, communications interface 280 includes an RF transceiver anddigital control circuitry. However, other components may also beassociated with a transceiver and/or other circuits. Communicationsinterface 280 is powered from rectifier and switch circuit 230 via lineLOAD_PWR and is configured to provide status signal COM_STAT to indicatean operational status such as failure of back-haul 294, the number ofwireless devices associated with base station 200, power consumptiondata, and/or the like.

Power Controller Examples

FIG. 3 is a block diagram of power controller 310. Power controller 310includes processor 314, battery circuit interface 316, alternate powercontrol interface 318, and operation, management, and control (OMC)interface 320, and may be configured to receive or provide controlsignals 312. Power controller 310 may be employed as an embodiment ofpower controller 210 of FIG. 2.

As illustrated, processor 314 is configured to control the operations ofa rectifier and switch circuit (e.g., via control signal RECT_CTL) andan alternate power interface (e.g., via alternate power controlinterface 318 and control signal ALT_CTL). Processor 314 is furtherconfigured to provide a status signal to a remote system (e.g., via OMCinterface 320 and status signal STATUS). In addition, processor 314 mayalso be interfaced to a battery circuit (e.g., via battery circuitinterface 316, string sense signals STR_SNS, and string enable signalsSTR_EN) to control the operations of battery circuit, includingselective switching, charging, testing, and power failure handling ofbattery strings within a battery circuit as described in greater detailherein.

As illustrated, processor 314 is also configured to provide watchdogsignal WD to a watchdog circuit (not shown). The watchdog circuit may bearranged to reset the processor via the RESET signal if, for example,the watchdog signal WD remains unchanged for a predefined duration. Inother embodiments, internal watchdog circuits, and/or the like, may alsobe employed.

Processor 314 is further configured to receive configuration signalCONFIG to represent a hardware configuration, to set various thresholdlevels, and/or the like. Any number of configuration signals may beprovided. In one embodiment, configuration signals are employed torepresent the number and/or types of rectifiers in the rectifier andswitch circuit, the type of alternate power source coupled to thealternate power interface, the number of battery strings in the batterycircuit, the types of batteries in the battery circuit, the capacitiesof batteries in the battery circuit, and/or the like. As anotherexample, a configuration signal may be provided to indicate the loadcapacity of the rectifiers so that processor 314 may more accuratelydetermine the number of active rectifiers for providing efficientrectification. As yet another example, a configuration signal may beprovided to indicate the design voltage of the battery circuit so thatprocessor 314 may more accurately estimate the charge on the batterycircuit from the battery circuit output voltage.

Configuration signal CONFIG may be provided from a switch (e.g., a DIPswitch), from pull-up resistors, from pull-down resistors, from jumpers,and/or the like. Alternatively, similar configuration information may beread by processor 314 from a memory or be received from anotherprocessor.

Processor 314 is also configured to receive various status signals asillustrated in FIG. 3. For example, signals COM_STAT and RECT_STAT maybe employed to respectively represent the status of the communicationsinterface and of the rectifier and switch circuit. Likewise, signalSTR_SNS may be employed to represent conditions of each of the stringsof the battery circuit. Also, signal RESET may be employed to resetand/or hold processor 314 in reset. Finally, control signal OVER_CURRENTmay be employed to represent an over-current condition of the batterycircuit, of the rectifier and switch circuit, and/or the like.

Processor 314 may be a microprocessor, a microcontroller, a digitalsignal processor (DSP), and/or the like. However, in other embodiments,digital logic, analog logic, combinations of digital logic and analoglogic, and/or the like may also be employed instead of a processor. Forexample, such embodiments may be implemented in a field-programmablegate array (FPGA), in an application-specific integrated circuit (ASIC),in other programmable logic devices (PLDs), and/or the like.

Battery circuit interface 316 is configured to interface processor 314to a battery circuit 260 of FIG. 2. For example, battery circuitinterface 316 interfaces string sense signals STR_SNS from batterycircuit 260 to processor 314 (e.g., to sense conditions of each stringof battery circuit 260) and interfaces power controller 310 to stringenable signals STR_EN (e.g., to select which strings of battery circuit260 are coupled to rectifier and switch circuit 230). For example,battery circuit interface 316 may include multiplexers, drivers,buffers, logic gates, analog circuits, and/or other logic or circuitryto perform sampling, multiplexing, demultiplexing, conversion, and/orthe like. As one example, battery circuit interface 316 includes anarray of analog to digital converters (ADCs) that are configured todigitize each of string sense signals STR_SNS and drivers configured todrive each of string enable signals STR_EN.

Alternate power control interface 318 is configured to interfaceprocessor 314 to alternate power interface 250 of FIG. 2. In oneembodiment, alternate power control interface 318 includes a relay, alevel-shifter, a driver, a buffer, an inverter, logic gates, and/or thelike that are configured to provide control signal ALT_CTL based, atleast in part, on the output of processor 314.

OMC interface 320 is configured to interface processor 314 to a remotesystem and to provide operational data regarding the base station and/orthe base station power system to the remote system. OMC interface 320may include drivers, buffers, inverters, logic gates, network interfaceunits, multiplexers, and/or the like. Likewise, OMC interface 320 may beconfigured to multiplex the STATUS signal onto the back-haul or mayprovide the STATUS signal as a discrete signal.

Battery Circuit Examples

FIG. 4 is a schematic diagram of a suitable battery circuit 460. Asillustrated, battery circuit 460 includes four battery strings461A-461D. Each battery string in turn comprises a string connectionswitch 463, one or more batteries 462, a fuse 464, and a sensor 465.Although four battery strings are shown, two or more battery strings maybe employed in battery circuit 460. Battery circuit 460 may be employedas an embodiment of battery circuit 260 of FIG. 2.

As discussed above with respect to FIG. 1, battery circuit 460 may beemployed in systems other than the base station or other communicationssystems of FIGS. 1-3. For example, battery circuit 460 may be employedin, or with, any system employing a backup or other battery circuit.

As shown, a battery string 461 comprises two or more batteries 462arranged in a serial fashion. Although FIG. 4 shows four batteries 462per battery string, any number of batteries may be employed per batterystring, and the various battery strings in a battery circuit 460 maycomprise different numbers of batteries per battery string. In oneexample, each battery string has four serially connected batteries thattogether form a negative 48 volt (V) string that has an approximatesuitable float voltage of 54 V. In one implementation, a battery string461 comprises serially connected absorbed glass mat (AGM) batteries thatare sealed valve-regulated, such as the SBS-S series or VRLA batteriesavailable from Storage Battery Systems® Inc. In another implementation,a battery string 461 comprises serially connected carbon nanotube (CNT)batteries. However, other batteries and/or energy storage devices suchas other types of AGM batteries, gel cell batteries, other deep cyclebatteries, flooded lead-acid batteries, nickel-metal-hydride batteries,nickel-cadmium batteries, lithium-ion batteries, lithium-polymerbatteries, alkaline batteries, capacitors, and/or the like, may also besuitably employed.

Each battery string 461 comprises a string connection switch 463configured to selectively connect and disconnect the one or moreserially connected batteries 462 in the battery string to a batterycircuit node carrying the battery power signal BAT_PWR. As shown, astring connection switch is controlled by a string enable signal STR_EN(e.g., the string connection switch of battery string 461A is controlledby the string enable signal STR_EN_A). As described previously, thebattery circuit node carrying battery power signal BAT_PWR may beconnected to a rectifier and switch circuit 230 to route battery powerto communications interface 280 or other loads and/or to charge one ormore battery strings (e.g., from primary power interface 240). Thus thestring connection switches 463 permit individual battery strings461A-461D to be selectively discharged and/or charged via various stringenable signals STR_EN. A string connection switch 463 may be implementedby a switching device of any type (e.g., field-effect transistors,insulated gate bipolar transistors, junction field-effect transistors,bipolar-junction transistors, relays, transmission gates, etc.).

During a particular time period, one or more battery strings 461 may bemaintained as an “active” string and one or more other strings may bemaintained as a “parked” string. Active strings are connected to thebattery circuit node and maintained regularly (e.g., daily) orcontinuously with a charging float voltage source or other type ofmaintenance source suitable for maintaining the active strings at ornear full charge. Unless a specified charging, testing, or power failureevent occurs, parked strings are strings of batteries that remaindisconnected from the battery circuit node and the floating voltagesource. Parked strings are thus typically charged less frequently thanactive strings (e.g., on an “as-needed” basis when their voltage and/orestimated charge falls below a threshold value) and thus may be onlypartially charged at a given time (e.g., charged to 95% capacity).

Power controller 210 may determine a suitable number of battery strings461 to maintain in active status based on factors such as the estimatedpeak and/or average power needed by battery loads such as thetelecommunication interface, cooling system (not shown), and powercontroller; the voltages of various battery strings; the estimatedand/or expected capacity of the various battery strings; the estimatedor measured charging, discharging, and self-discharge rates of thevarious strings; and/or the condition of the various strings (e.g., ifthey have failed during prior testing). For example, power controller210 may choose to maintain enough active strings to satisfy the peakpower demands imposed by a telecommunications interface and associatedcooling system. In the example, power controller 210 may maintain morebattery strings in active status during summer months, when a coolingsystem requires more power.

Since the various battery strings 461 are individuallyconnectable/disconnectable, power controller 210 may rotate a givenbattery string into and out of active service. Power controller 210 mayrotate batteries on the basis of numerous factors including a fixedamount of time; the voltages of various battery strings; the estimatedor measured discharge level of the various battery strings; theestimated peak and/or average power needed by battery loads such as thetelecommunication interface, cooling system, and power controller; theestimated and/or expected capacity of the various battery strings; theestimated or measured charging, discharging, and/or self-dischargingrate of parked strings; and/or the condition of the various strings,including cumulative time in active service.

Rotating strings may result in many benefits. By rotating strings thesystem reduces unnecessary charging, resulting in lower powerexpenditures and less heat in the battery compartment. Also, each stringmay spend less time on a float voltage source, so the average batterylife may increase, and batteries are less likely to become unbalanced.The system may test batteries without discharging the batteries, whichalso improves the average life of the batteries. Finally, the system mayremotely test the various battery strings and, when strings fail, simplysend an alert and rotate alternate strings into active service, thusreducing the need for service calls.

When a new battery string 461 or battery 462 is deployed within abattery circuit 460, the power controller 210 may record the time and/ordate of deployment in an index or other data structure that correlatesdeployment times, failure times, applicable warranty periods, serialnumbers, and/or other similar information. Alternatively, oradditionally, power controller 210 may send this information to a remotemonitoring location. In this way, power controller 210, via regulartesting of the battery strings 461, may detect when a battery string 461or a battery 462 failure indicates that a warranty remedy is available(e.g., a free replacement battery, free service, a refund, etc.) and maytake steps towards claiming any warranty remedy (e.g., by notifying aremote monitoring location of the warranty remedy and/or otherwise).

In an illustrative implementation, battery circuit 460 comprises tenbattery strings A-J. In one example, string A may be active for May,then string B may be active for June, and in July, due to higher coolingrequirements, strings C and D are active, and so on. In a secondexample, string A may be active until parked strings B-J requirecharging, e.g., because a parked string voltage indicates that theparked string has fallen below a threshold charge (e.g., 95% charge). Inthe second example, at the completion of a charging of strings B-J,string A may then be rotated from active status to parked status andstring B may be rotated from parked status to active status.

Although only a subset of active strings are maintained at a given time,during a power failure, power controller may selectively press thepartially charged parked strings into service to provide additionalpower to communications interface 280 and/or other battery loads.

When power controller 210 connects a parked string to the batterycircuit node (e.g., for rotation, for as-needed charging, or during apower failure), it must ensure that the parked string has approximatelythe same voltage as other battery strings that are already connected tothe node. Otherwise arcing and/or other dangerous conditions mightresult from the mismatched batteries. Thus, as described herein, powercontroller may actively adjust or wait for the voltages of connectedbattery strings to reach or “intercept” the voltage of a parked stringbefore connecting the parked string.

In some examples, string connection switch 463 may be a multi-positionswitch configured to also selectively connect and disconnect the one ormore serially connected batteries 462 in a battery string 461 to analternate charging circuit node carrying the alternate charging signalALT_CHARGE_PWR. In such examples, string connection switch 463 may beutilized to selectively couple a parked battery string to the alternatecharging signal so that the parked battery string may be charged usingan alternate energy power source such as alternate power source 290. Insome implementations, under the direction of power controller 210,rectifier and switch circuit 230 may route power generated by alternatepower source 290 that exceeds the operational needs of the base station(e.g., output that is higher than that needed by communicationsinterface 280 or another load) over the ALT_CHARGE_PWR signal to one ormore parked battery strings so that the parked strings may be charged bythe excess power that might otherwise be wasted.

As shown, a battery string 461 also comprises a fuse 464 in series withbatteries 462. Fuse 464 protects battery string, rectifier and switchcircuit 230, a load of the battery circuit 460 (e.g., communicationsinterface 280), and/or other system components from out-of-range orexcessive currents. Fuse 464 may also permit power controller 210 todetect anomalous current conditions that occur in the string and/or testa battery string for failures. For example, power controller 210 mayrepeatedly reset a fuse to test a battery string. If the fuse repeatedlytrips after these resets, power controller 210 may determine that thebattery string has failed and take steps, such as holding the fuse openand/or sending a failure notification.

Fuse 464 may be implemented with any suitable fuse, breaker, or anyother type of device having a suitable break/trip point, tolerance, etc.In one implementation, fuse 464 may be a breaker capable of being resetvia an electrical control signal. For example, fuse 464 may be amotorized or other remotely resettable on/off breaker controllable by acontrol signal that does not require power flowing through a batterystring to hold its position. In some implementations, a motorizedbreaker used as a fuse 464 may have a “Z” shaped profile. Although notshown in the Figures, power controller 210 may be communicativelycoupled to a motorized breaker used as a fuse 464 so that powercontroller 210 may control the operation of the breaker via controlsignals. In still other implementations, fuse may be combined withstring connection switch 463.

As shown, a battery string 461 also comprises a sensor 465. AlthoughFIG. 4 shows a single sensor 465 connecting the batteries 462 and fuse464 to a ground reference, more than one sensor may be employed in abattery string and/or a sensor may be located at another location in thebattery string (e.g., farther from ground reference). In someimplementations, sensor 465 is a current sensor (e.g., sense resistor,Hall effect sensor, current shunt, optoisolator, ADC, etc.) to enablemonitoring of instantaneous current. However, sensor 465 may alsoinclude or be a voltage sensor and/or power sensor to enable monitoringof instantaneous voltage, power, or both. Sensor 465 may also implementvarious operations, such as averaging, integrating, differentiating,and/or the like to estimate or calculate other values such as averagepower, average current, expended charge, remaining charge, etc. in abattery string.

As shown, sensor 465 provides a string sense signal STR_SNS, which asdescribed previously may be input to power controller 210. For example,string sense signals STR_SNS may be employed to indicate the outputvoltage of the battery strings 461A-461D, the output voltage of anindividual battery 462 within a battery string 461, an input/output(I/O) current, I/O power, and/or the like. Power controller 210 may beconfigured to determine conditions relating to the state of batterycircuit 460 and/or its components from string sense signals STR_SNS. Forexample, power controller 210 may be configured to evaluate and/oranalyze the string sense signals STR_SNS to determine failure conditions(e.g., failed batteries or failed battery strings); the open or closedstate of fuses 464; the approximate charge level of a battery 462,battery string 461, and/or battery circuit; the output voltage of abattery and/or battery string, and so forth. Information from sensors465 and conveyed by string sense signals STR_SNS may be employed bypower controller 210 to perform processes such as those discussed below.

Although not shown, battery circuit 460 may additionally comprise one ormore temperature sensors configured to provide measured temperatures inor near the battery circuit 460 to power controller 210 so that powercontroller 210 may calculate or adjust operating, charging, or testingvalues and/or other parameters that are temperature-dependent (e.g.,suitable float voltages, charging voltages or currents, estimatedbattery charge, etc.).

Although particular aspects of battery circuit 460 are illustrated anddescribed herein, other battery circuits may differ in any number ofaspects. For example, other battery circuits may include additionaland/or different elements, be configured in other configurations,provide and/or enable additional and/or other functionality, and/or thelike. Other suitable battery circuits may be as described in U.S.application Ser. No. 12/365,165, entitled “BATTERY MONITORING SYSTEM,SUCH AS FOR USE IN MONITORING CELL SITE POWER SYSTEMS,” filed on Feb. 3,2009, which is hereby incorporated by reference.

Example Processes

FIG. 5 is a logical flow diagram of process 500 for managing a batterycircuit, FIG. 6 is a logical flow diagram of process 600 for chargingand/or testing a battery circuit, and FIG. 7 is a logical flow diagramof process 700 for handling a power failure. Each of these Figures willnow be discussed in detail. For clarity, processes 500, 600, and 700 aredescribed below as being performed by power controller 210 of FIG. 2.However, processes 500, 600, and 700 may also be performed by powercontroller 310 of FIG. 3 or its processor 314, another component of basestation 100, or another remote component or remote monitoring location.

Processes 500, 600, and 700 may also be performed by other processors,by other components, or in other systems, whether or not suchprocessors, components, or systems are described herein. Processes 500,600, and 700 may also be embodied on processor and/or computer readablemedia such as non-volatile memory, volatile memory, and/or the like.These flow diagrams do not show all functions or exchanges of data, butinstead they provide an understanding of commands and data exchangedunder the system. Those skilled in the relevant art will recognize thatsome functions or exchange of commands and data may be repeated, varied,omitted, or supplemented, and other (less important) aspects not shownmay be readily implemented.

Aspects of the invention may be stored or distributed on tangible ornon-transitory computer-readable media, including magnetically oroptically readable computer discs, hard-wired or preprogrammed chips(e.g., EEPROM semiconductor chips), nanotechnology memory, biologicalmemory, or other data storage media. Alternatively, computer implementedinstructions, data structures, screen displays, and other data underaspects of the invention may be distributed over the Internet or overother networks (including wireless networks), on a propagated signal ona propagation medium (e.g., an electromagnetic wave(s), a sound wave,etc.) over a period of time, or they may be provided on any analog ordigital network (packet switched, circuit switched, or other scheme).

The process 500 of FIG. 5 begins at decision block 510, where powercontroller 210 determines whether it detected an event that requiresfurther action by power controller 210. To make the determination, powercontroller 210 may perform internal calculations, access stored or setvalues, and/or evaluate various received control signals, input signals,and status signals, including reset signal RESET, configuration signalCONFIG, control signal OVER_CURRENT, and status signals COM_STAT,RECT_STAT, and STR_SNS. If power controller 210 does not detect an eventthat requires further action, it repeats block 510 by continuing tomonitor for events. Otherwise process 500 proceeds to block 520.

Several types of events may require further action by power controller210. As a first example, power controller may determine that one or morebattery strings or batteries reached a predetermined threshold voltage,estimated charge or discharge, instantaneous or average I/O current,instantaneous or average I/O power, etc. To illustrate, power controller210 may determine that a parked battery string reached or fell below athreshold voltage, indicating a need for charging and/or testing of thebattery circuit 260. As a second example, power controller may determinethat a fuse 464 tripped, e.g., indicating an excessive or anomalouscurrent in a battery string. As a third example, power controller maydetermine that the present time and/or date requires additionalscheduled action. As an illustration, power controller 210 may determinethat it is an “off-peak” time when power rates are lower or cheaper andthus an appropriate time to charge the battery circuit. As anotherillustration, power controller may determine that a specified number ofdays has elapsed since power controller last charged the batterycircuit. As a fourth example, power controller may determine thatprimary power and/or alternate power sources failed. As a fifth example,power controller may determine that primary power and/or alternate powercame back online after a failure. As a sixth example, some combinationof previous examples may occur (e.g., a battery string may reach athreshold voltage and it may be an off-peak time suitable for charging).These examples are intended to be illustrative, not exhaustive and arediscussed in greater detail herein.

At decision block 520, power controller 210 determines whether thedetected event indicates that power controller should test the batterycircuit for failures, damage, or other undesirable conditions (e.g.,unbalanced batteries). If a battery test event occurs, process 500proceeds to block 530, where power controller 210 performs a batterytest process, and then process 500 repeats starting at block 510.Otherwise, process 500 proceeds to block 540. The type of test processperformed at block 530 may depend on the event that triggered testing.

Power controller 210 may determine that it should perform testing usingthe present state of one or more battery strings as determined by thestatus signals STR_SNS. As a first example, power controller maydetermine that testing is required if it estimates that the total chargeremaining in battery circuit 260 falls below a threshold value; it mayestimate the total charge by evaluating the output voltages of thebattery strings and/or other parameters such as the temperature and/ortype of battery used. As a second example, power controller maydetermine that it should perform testing if the voltage of a parkedbattery string (or parked battery) reaches or falls below a thresholdvoltage. In some implementations, power controller may set a thresholdvoltage by first calculating a baseline voltage for the battery stringbased on the type of batteries in the string, the temperature of thebattery compartment or other environmental conditions, and/or the timeelapsed since the string was last fully charged, and then setting thethreshold as a particular percentage of the determined baseline voltage.In some examples, power controller uses a float voltage suitable for thepresent conditions as the baseline voltage. For example, in someimplementations, the threshold value may be chosen as 98% of a suitablefloat voltage. Alternatively, power controller may set the thresholdvoltage to a value that corresponds to a particular level of estimatedcharge stored in a battery string. To calculate a threshold voltage insuch implementations, power controller may evaluate the type ofbatteries in the string, the temperature of the battery compartment,and/or other environmental conditions. For example, power controller mayset a threshold voltage that corresponds to the battery string havingapproximately 98% of its total charge capacity.

In other examples, power controller 210 may determine that it shouldperform testing if a fuse 464 trips, which indicates unusual current orother conditions in a battery string. Power controller 210 may alsoinitiate testing if string sense signals STR_SNS indicate an anomalouscurrent profile in a battery string. For example, power controller 210may initiate testing if a charging or discharging current for a batterystring is unusual, e.g., significantly higher or lower than those seenin other strings or as compared to a reference value. As yet anotherexample, power controller may initiate testing if it determines that aperiodic or nonperiodic scheduled testing is due (e.g., a testingmandated by an applicable policy or configuration setting). Powercontroller 210 may trigger testing if it determines that the primarypower and/or alternate power came back online after a failure, and thus,the battery circuit should be tested to ensure that it was not damagedor otherwise compromised during the power failure.

FIG. 6 describes one suitable battery test process that may be performedat block 530 in tandem with battery circuit charging 550. Powercontroller 210 may perform the process of FIG. 6 when power controller210 determines that one or more parked battery strings have a voltagebelow a threshold voltage, at a predetermined time (e.g., at thebeginning of an off-peak time), or when a combination of these eventsoccur (e.g. when a parked battery string has a voltage below a thresholdvoltage and it is an off-peak time).

Alternatively, or additionally, power controller 210 may perform otherbattery circuit testing procedures at block 530. For example, if amechanically resettable fuse 464 (e.g., a resettable breaker) associatedwith a battery string trips to an open position, power controller 210may wait a first predetermined amount of time before closing the breakerusing a control signal and then determine whether the breaker remainsclosed for a second predetermined amount of time. Whether the powercontroller 210 determines that a mechanical fuse 464 repeatedly tripsduring a short time window (e.g., trips open three times in under 30seconds), the power controller 210 may determine that its associatedbattery string is defective.

If power controller 210 determines that a battery string or battery isdefective at block 530, it may report the defective string or battery toa remote monitoring location (e.g., by sending a message via OMCinterface 320 using the STATUS signal) at which the error may be logged,a trouble ticket opened, a technician dispatched, a warranty remedyclaimed, and/or the like. Power controller may also take other actions,such as disconnecting the defective string from the battery circuit nodeusing a string enable signal STR_EN, updating power controller'shardware configuration (e.g., to indicate that the string is defective),determining whether a warranty remedy is available due to the failure(e.g., using an index or other data structure related to warranties asdescribed previously and/or by querying a remote monitoring location),taking steps towards claiming an available warranty remedy, and/or othersuitable actions.

At decision block 540, power controller 210 determines whether an eventoccurred that indicates that power controller should perform charging ofthe battery circuit. If a battery charging event occurs, process 500first proceeds to block 550, where power controller performs a batterycharging process, and then repeats starting at block 510. Otherwise,process 500 proceeds to block 560. Battery charging events include ascheduled charging event, the return of primary power and/or alternatepower after a power failure, the remaining estimated charge in batterycircuit (as determined from output voltages of the various batterystrings) falling below a threshold value, and one or more batterystrings or batteries reaching a threshold voltage (or other thresholdvalue, e.g., threshold charge or I/O power) as described previously withrespect to block 520.

FIG. 6 describes one suitable battery charging and testing procedurethat may be performed at block 550. Any other suitable battery chargingprocess may be performed at block 550, however, including chargingprocesses that do not also implement testing. For example, powercontroller 210 may perform only the “top off” charging described withrespect to block 660 of process 600.

At decision block 560, power controller 210 determines whether an eventoccurred that indicates that power controller should rotate the variousbattery strings. Rotation of battery strings comprises changing whichbattery strings are active and which are parked by using the stringenable signals to connect one or more strings to the battery circuitnode and/or to disconnect one or more other strings from the node. Asdescribed previously with respect to FIG. 4, power controller 210 mayperform battery rotation when a predetermined period elapses or upon aspecified schedule (e.g., after a particular battery string has beenactive for 30 days), when one or more battery strings reaches aparticular state (e.g., after a parked battery string reaches athreshold voltage or other threshold value, or when an active stringfails), in conjunction with testing and/or charging of the batterycircuit, after a primary or alternate power source comes online after afailure, and/or upon the occurrence of other types of events.

If power controller 210 determines that a battery rotation eventoccurred, process 500 proceeds to block 570, where power controllerperforms a battery rotation process, and then repeats starting at block510. Otherwise, process 500 proceeds directly to block 580. At block570, power controller typically performs calculations, accesses storedor received configuration parameters, and evaluates string sense signalsSTR_SNS and other status signals in order to determine which batterystrings should be connected and which strings should be disconnectedduring a rotation. As described previously with respect to FIG. 4, powercontroller 210 may evaluate several factors when selecting how many andwhich battery strings to rotate into active service; for brevity, thosefactors are not repeated here. In some implementations, power controllermay implement a first-on, first-off approach to rotating battery stringsthat sequentially rotates in the various battery strings. In otherimplementations, power controller may replace an active string withwhatever battery string has the lowest accumulated time in activeservice.

To rotate battery strings at block 570, power controller 210 may simplydisconnect all currently active strings from the battery circuit nodeand then connect one or more currently parked strings to the node viastring enable signals STR_EN. However, unless the connected batterystrings are equalized, arcing or other undesired results will occur.Alternatively, power controller may instruct the rectifier and switchcircuit 230 (e.g., via control signal RECT_CTL) to reduce the voltageprovided to the node to a value below the voltages of the incomingstrings that are to be rotated into an active state. When the voltageacross the currently active strings intercepts an incoming string, thepower controller may then connect the intercepted incoming string to thenode using a string enable signal STR_EN. Once all the incoming stringsare connected to the node in this manner, the power controller may theninstruct the rectifier and switch circuit to raise the voltage providedto the node to a float value that is suitable for the type of batteries,the temperature of the batteries, and/or other conditions. Either beforeor after raising the voltage, power controller 210 may disconnect thepreviously active strings using string enable signals STR_EN.

In some examples, a single event may trigger a power controller toperform more than one of battery charging, testing, and/or rotation,resulting in the substantially simultaneous performance of blocks 530,550, and/or 570. For example, power controller may initiate batterycharging, testing, and rotation when the voltage of a parked batterystring reaches or falls below a threshold voltage (e.g., a thresholdvoltage that indicates more than 98% discharge) and/or during anoff-peak period.

At decision block 580, power controller 210 determines whether anexternal power source has failed, i.e., whether primary power signalPRI_IN and/or alternate power signal ALT_IN cannot provide sufficientpower to operate communications interface 280 and/or power controller210. Power controller 210 may perform this determination based on statussignal RECT_STAT, a status signal from primary power interface 240,and/or the like. If a power failure occurs, process 500 proceeds toblock 590, where power controller performs a power failure handlingprocess and then repeats starting at block 510. Otherwise, process 500directly repeats starting at block 510. When an external power sourcefails, power controller 210 may instruct rectifier and switch circuit230 to route battery power from the battery circuit node tocommunications interface 280, power controller 210, and/or other loads.Suitable methods for performing power failure handling are described ingreater detail with respect to FIG. 7.

At block 595, power controller 210 determines if the power failure hasended. If is has, process 500 repeats starting at block 510. Otherwise,process 500 repeats starting at block 590.

FIG. 6 is a logical flow diagram of a process 600 for charging and/ortesting a battery circuit. Before process 600 begins, power controller210 may maintain one or more active battery strings (e.g., 461A) in afloating state, at approximately a float voltage, while one or moreparked strings (e.g., 461B, 461C, 461D) are disconnected from thebattery circuit node. To do so, power controller 210 may maintain theconnection of the active string(s) to the battery circuit node and, whenprimary and/or alternate power sources are available, instruct therectifier and switch circuit 230 to provide a float voltage to theactive strings (e.g., provide a voltage sufficient to keep the activestrings at approximately full charge under present conditions, includingthe temperature in the battery circuit).

Table 1 shows example states of four battery strings prior to theprocess of FIG. 6. The example values shown in Table 1 will bereferenced in further discussions herein to illustrate various conceptsrelated to FIG. 6.

TABLE 1 Illustrative example of the state of four battery strings beforeprocess 600. String Name Voltage Connection Status Charge Status A  54 VActive Charged B 52.2 V Parked Uncharged C 49.0 V Parked Uncharged D48.5 V Parked Uncharged

Table 1 provides just one example of starting states. In some otherexamples, prior to the process 600, the various battery strings may havevery different states from those shown in Table 1. For example, if arecent power failure occurred, all of the strings may be active and/ormay have roughly equal output voltages.

Process 600 begins at block 610, when power controller 210 selects atarget string that the power controller will next charge and test. Insome implementations, power controller 210 selects the parked stringthat is (1) as yet uncharged and (2) has the highest voltage among allof the parked and uncharged strings (e.g., in Table 1, string B). Inother implementations, power controller may utilize any other suitableselection method.

Prior to block 620, power controller 210 may adjust the voltage and/orcurrent applied to the battery circuit node so that the voltage acrossthe active strings will eventually reach or “intercept” the voltage ofthe target string. To do so, in one implementation, power controller 210may instruct rectifier and switch circuit 230, via control signalRECT_CTL, to reduce the voltage applied to the battery circuit node. Inresponse to a lower applied voltage, the voltage of the active batterystrings may drop, partly due to the active strings burning throughsurface charge. Power controller 210 may select the applied voltagebased on the voltage of the target battery string, the voltage of theactive strings, the voltage of another parked battery string,environmental conditions (e.g., temperature), the type of battery used,a threshold voltage (e.g., a threshold voltage as described previously),and/or similar factors. In one example, power controller selects anapplied voltage that is a predetermined amount (e.g., 1 V) lower thanthe voltage of the target string. For example, if string B shown inTable 1 is selected as the target string, the applied voltage may be51.2 V, one volt below the voltage of string B. One having skill in theart will appreciate that many different other applied voltages may bechosen so long as the applied voltage will cause the voltage of theactive strings to intercept the voltage of the target string.

At block 620, when power controller 210 determines that the voltage ofthe active strings approximately reaches or intercepts the voltage ofthe target string, the power controller connects the target string tothe battery circuit node via a string enable signal STR_EN. To determinewhen to connect the target string, power controller 210 may monitor thestring sense signals STR_SNS corresponding to the target and activestrings. In the Table 1 example, if string B is the target string, andstring A is an active string, power controller 210 may monitor stringsense signals STR_SNS_B and STR_SNS_A to see when these values areapproximately equal. One having skill in the art will appreciate thatdue to various battery effects, the voltages and/or currents of theactive and/or target strings (e.g., strings A and B) may vary rapidlyand/or vary in a nonlinear or unstable fashion as power controller 210attempts to intercept the target string and connect it to the node orshortly after it connects the target string. Due to rapid changes,during block 620, power controller 210 may monitor the string sensesignals repeatedly and/or take additional steps to achieve equalvoltages across the active and target strings and/or to prevent damageto the battery strings and/or other components. For example, the powercontroller 210 may make additional adjustments to the applied voltage,flip a fuse or breaker to prevent or respond to a high current through abattery string, and/or take other suitable steps.

Once the target string is connected, at block 630, power controller 210initiates partial charging and testing of the target string. To do this,power controller may instruct rectifier and switch circuit 230, viacontrol signal RECT_CTL, to raise the voltage applied to the batterycircuit node to a suitable charging voltage selected on the basis of thetype of battery, temperature, and/or other conditions in order topartially charge the target battery string. In some implementations,power controller may instruct rectifier and switch circuit 230 toprovide charging in a current limiting mode and/or otherwise specify afixed current and/or current profile. For example, power controller mayinstruct rectifier and switch circuit 230 to provide five minutes of 200A charging current and then fifteen minutes of 50 A charging current. Asanother example, power controller may instruct rectifier and switchcircuit 230 to provide 15 minutes of 38 A charging current. Rectifierand switch circuit may charge the target string for a specified durationof time. Alternatively, or additionally, power controller may apply acharging voltage until the target string reaches a specified voltage,I/O current, I/O power, estimated charge, or other condition, asdetermined by a string sense signal STR_SNS.

At block 630, while the target string is connected and is activelycharging, power controller 210 may take additional measurements of thestate of the target string by monitoring string sense signals STR_SNSfor anomalies indicative of a high open, failed battery, unbalancedbatteries, a bad connection, or other undesirable conditions. As a firstexample, if rectifier and switch circuit 230 is directed to provide aspecific charging current (e.g., 200 A) during the first part of block630, power controller 210 may monitor the string sense signal STR_SNSassociated with the target string to identify the I/O current and/orpower of the target string that is responsive to the specific chargingcurrent. If the responsive current is unexpectedly low (e.g., ascompared to other strings), power controller 210 may determine that thetarget battery string has an anomalous “high open.” As a second example,power controller may monitor the string sense signal STR_SNS associatedwith the target string to identify the instantaneous and/or average I/Ocurrent and/or power drawn by the target string during some period ofcharging, such as the end of charging (e.g., during the last 30 secondsof charging at block 630). Power controller may then compare the drawnI/O current/power with the current/power drawn by other strings or witha reference current/power and/or may determine whether non-common-modeAC noise is present in the measurement. By comparing the current draw ofone battery string against another battery string in similar conditions(e.g., similar temperature), power controller 210 may determine whetherthe target string draws a charging current that is anomalous for theconditions. As a third example of testing, power controller maydetermine whether the target string has a substantially different(e.g., >5% different) discharge, charge, or self-discharge rate ascompared to other strings. Power controller 210 may determine theserates from the time elapsed during charging and/or the voltage and/orcurrent profile of the string during discharging and/or charging. As afourth example of testing, as described previously, power controller mayalso determine whether a fuse 464 (e.g., a mechanically resettablebreaker) repeatedly trips during charging, indicating an atypicalcharging current. However, power controller may perform any suitabletesting processes at block 630.

If at block 630 power controller 210 detects that the target string hasapparent defects such as a high open, different charging, discharging orself-discharging rates, or an anomalous charging current/power, powercontroller 210 may report that the string is apparently defective to aremote monitoring facility (e.g., by sending a message via OMC interface320 using the STATUS signal) at which the defect may be logged, atrouble ticket opened, a technician dispatched, and/or the like. Powercontroller may also take other actions, such as disconnecting thedefective string from the battery circuit node using a string enablesignal STR_EN, updating its hardware configuration (e.g., to indicatethat the string is apparently defective), refraining from charging thestring in the future, and/or other suitable actions.

At block 640, when charging and/or testing of the target string iscomplete, power controller 210 disconnects the target string from thebattery circuit node using a string enable signal STR_EN.

At decision block 650, power controller 210 determines whether chargingand testing of all of the battery strings is complete. If some batterystrings have not yet been charged/tested, process 600 repeats startingat block 610, so that the next uncharged/untested string may becharged/tested.

In the example of Table 1, after blocks 610-650 have been repeated threetimes, the state of various battery strings might be as shown in Table2.

TABLE 2 Illustrative example of the state of four battery strings afterthree iterations of blocks 610-650. String Name Voltage ConnectionStatus Charge Status A 53.5 V Active Partially charged B 53.2 V ParkedPartially charged C 53.4 V Parked Partially charged D 52.9 V ParkedPartially charged

Once all of the battery strings have been partially charged/tested viablocks 610-640, the process proceeds to block 660. At block 660 powercontroller 210 “tops off” the charge on all of the battery strings byapplying a suitable float voltage simultaneously to all the batterystrings. Power controller may determine a suitable float voltage basedon the type of battery and related battery specifications, batterytemperature (or other environmental conditions), and/or any othersuitable criteria. Before applying a suitable float voltage to all thestrings, power controller performs actions similar to those describedwith respect to blocks 610-620 to connect the various strings to thebattery circuit node. For example, power controller 210 may repeatedly:identify a target string, select and apply a voltage to the batterycircuit node to cause the voltage of the connected strings to interceptthe voltage of the target string or target voltage, and then connect thetarget string at approximately the time when the voltages intercept. Inone implementation, power controller 210 connects a battery string byselecting the unconnected string having the highest voltage of allunconnected strings, adjusting (e.g., lowering) the applied voltage tointercept the target string, and connecting the target string. Powercontroller then repeats this process by selecting the unconnected stringhaving the next highest voltage, intercepting it, and connecting it,etc. To illustrate, in the example of Table 2, power controller mayidentify string C, apply 53.3 V to the battery circuit node, and connectstring C when the voltage of string A drops to approximately 53.4 V;identify string B, apply 53.1 V to the node, and connect string B whenthe voltage of strings A and C drop to approximately 53.2 V; andidentify string D, apply 52.8 V to the node, and connect string D whenthe voltage of strings A, B, and C drops to approximately 52.9 V. Asanother example, power controller may simply apply a 52.8 V voltage (oranother voltage lower than any of the strings) continuously to thebattery circuit node and connect strings C, B, and D in turn as each oftheir voltages is intercepted by string A.

Once all of the strings are connected in this fashion, power controller210 may instruct rectifier and switch circuit 230 to raise or adjust thevoltage to a suitable level or target voltage for float charging; powercontroller 210 may also instruct rectifier and switch circuit 230 tooperate in a current limiting mode. During float charging, powercontroller 210 may perform some or all of the testing describedpreviously with respect to block 630, since power controller 210 may bemost likely to detect errors as the batteries approach a full charge andtheir internal resistances decrease.

Power controller 210 may terminate the float charging of one or morebattery strings upon any suitable condition, including when a given timeperiod has elapsed, when one or more battery strings reaches aparticular condition or state (e.g., when a battery string has aparticular output voltage, I/O current, or estimated charge), and/orwhen the total charging current or power provided by the rectifier andswitch circuit 230 drops below a particular value that indicates thatall battery strings are fully charged. To terminate top-off charging,power controller may utilize string enable signals STR_EN to disconnectone or more strings from the battery circuit node. The various stringsmay be disconnected either simultaneously or at different times.

Although not shown, at block 660, when disconnecting the various batterystrings to terminate top-off charging, power controller may effectivelyrotate the battery strings (as described previously) by disconnecting apreviously active battery string and leaving a previously parked batterystring connected so that it may become active. To illustrate, in theexample of Tables 1 and 2, after block 660 is complete, the state of thevarious battery strings may be as shown in Table 3.

TABLE 3 Illustrative example of the state of four battery strings afterprocess 600. String Name Voltage Connection Status Charge Status A 54 VParked Charged B 54 V Active Charged C 54 V Parked Charged D 54 V ParkedCharged

Power controller 210 was previously described as charging and testingparked battery strings at blocks 610-650 by working from the parkedbattery string having the highest voltage down to the parked batterystring having the lowest voltage. To illustrate, in the example of Table1, string B may be charged first, then string C, then string D. In suchimplementations, the applied voltage used between blocks 610 and 620will generally remain equal and/or drop each time these blocks arerepeated so that the voltage of the active strings may intercept thenext target battery string. To illustrate, in the example of Table 1,between blocks 610 and 620, the power controller may apply 51.2 V whenconnecting battery string B, 48.0 V when connecting battery string C,and 47.5 V when connecting battery string D.

One having skill in the art will appreciate that parked battery stringsmay be charged and tested in any other suitable order, so long as thevoltage of the connected battery strings roughly intercepts the voltageof the target string at the time the target string is connected. Forexample, the power controller may charge and test the parked batterystrings by working from the parked battery string having the lowestvoltage up to the parked battery string having the highest voltage. Toillustrate, in this type of implementation, in the example of Table 1,string D would be charged/tested first, then string C, and finally,string B. In such implementations, the applied voltage used, betweenblocks 610 and 620 will generally remain equal and/or increase each timethese blocks are repeated so that the voltage of the active strings willintercept the next target battery string. To illustrate, in the exampleof Table 1, between blocks 610 and 620, the rectifier and switch circuit230 may apply 47.5 V when connecting battery string D, 48.0 V whenconnecting battery string C, and 51.2 V when connecting battery stringB.

Similarly, power controller 210 was previously described at block 660 asintercepting and connecting battery strings by working from the highestvoltage string to the lowest voltage. One having skill in the art willappreciate that at block 660, power controller may instead connectbattery strings to the battery circuit node in a different order, solong as the voltage of the connected battery strings roughly interceptsthe voltage of the target string at the time the target string isconnected. For example, in some implementations, power controller mayapply a voltage that is equal to or lower than the voltage of anydisconnected string, connect the lowest voltage string to the batterycircuit node when that string is intercepted, apply the suitablefloating voltage to the battery circuit node, and as the voltage of theconnected battery strings rises (due to the higher applied floatingvoltage), add additional battery strings as they are intercepted. Toillustrate, in the example of Table 2, power controller 210 may apply a51.9 V source to the battery circuit node and connect lowest-voltagestring D when active string A reaches 52.9 V. Then power controller 210may instruct rectifier and switch circuit 230 to apply a suitable floatvoltage (e.g., 54 V), causing the voltage of connected strings A and Dto rise and intercept the voltage of string B (which is then connected),and then finally intercept the voltage of string C (which is connectedlast).

FIG. 7 is a logical flow diagram of process 700 for handling a powerfailure. Before process 700 begins, power controller 210 may maintainone or more active battery strings (e.g., 461A) in a floating state, atapproximately a float or target voltage, while one or more parkedstrings (e.g., 461B, 461C, 461D) are disconnected from the batterycircuit node. To do so, power controller may maintain the connection ofthe active string(s) to the battery circuit node and, when primaryand/or alternate power sources are available, instruct the rectifier andswitch circuit 230 to provide a float voltage to the active strings(e.g., provide a voltage sufficient to keep the active string(s) atapproximately full charge under present conditions, such as temperaturein the battery circuit).

Table 4 shows example states of four battery strings prior to theprocess of FIG. 7. The example values shown in Table 4 will bereferenced in further discussions herein to illustrate various conceptsrelated to FIG. 7.

TABLE 4 Illustrative example of the state of four battery strings beforeprocess 700. String Name Voltage Connection Status Charge Status A  54 VActive Charged B 53.6 V Parked Uncharged C 53.8 V Parked Uncharged D53.5 V Parked Uncharged

As described previously, process 700 of FIG. 7 may be triggered whenpower controller 210 detects a power failure, e.g., if due to ablackout, primary power signal PRI_IN fails to provide sufficient powerto operate communications interface 280. As described previously inreference to block 580, when an external power source fails, powercontroller 210 may instruct rectifier and switch circuit 230 to routebattery power from the battery circuit node to communications interface280, power controller 210, and/or other loads. As a result of this loadon the battery circuit, the active batteries may begin to discharge, andthe voltage at the battery circuit node (and across the active,connected battery strings) will drop before and during process 700.

The process 700 of FIG. 7 begins at block 710, where power controller210 selects one or more parked strings as target strings. Typically,power controller selects the one or more parked strings that have thehighest voltages as compared to other parked strings. To illustrate, inthe example of Table 4, power controller may first select parked stringC, since it has the highest voltage of all of the parked strings, thenstring B, then string D. Additionally, or alternatively, at block 710,power controller may determine the number of strings to select and whichparked strings to select on the bases of time (e.g., time elapsed sincethe power failure), a voltage of a parked string, a voltage of an activestring, an estimated power or charge being drawn by the load, themeasured capacity of the various battery strings, the calculatedcapacity of the various battery strings, a condition of the parkedstrings (e.g., whether they have failed during prior testing), and/orthe expected capacity of the various battery strings. For example, atblock 710, power controller may estimate the current capacity of theactive strings and their rate of discharge based on the active strings'current voltage, the discharge current, the temperature, and specifiedmanufacturer and/or configuration parameters. As another example, powercontroller may determine that the current load necessitates the additionof one additional battery string, string C.

At block 720, power controller 210 utilizes one or more string enablesignals STR_EN to connect the selected target string(s). Powercontroller 210 connects a target string when its voltage is interceptedby the voltage of the active and connected battery strings, which isdropping due to the load.

At block 730, power controller 210 monitors the target string(s) andother strings that were previously connected to the battery circuit node(e.g., strings that were active before the power failure). For example,power controller 210 may monitor the string sense signals STR_SNS todetermine the voltage, I/O current, I/O power, and/or discharge rate ofthe target strings(s) and/or batteries therein so that power controllermay perform decision block 750 and repeat blocks 710 and 720 asnecessary.

In some implementations, at block 730 power controller 210 may alsomonitor the target string(s) and other connected strings to detectdischarge errors. For example, power controller 210 may determinewhether connected string(s) have different DC values, are experiencingfluctuations in their output voltage, have significant noise, or havesubstantially different discharge rates. Power controller may alsodetermine whether a connection is arcing and/or whether there areanomalous currents that might damage the load, a battery string, and/oranother component. As yet another example, power controller 210 maydetermine whether a fuse 464 in a battery string has tripped open aftera target string was added. If a fuse is a resettable breaker, powercontroller 210 may close the breaker after a predetermined amount oftime.

Power controller 210 may determine that a discharge error occurred ifthere is a difference of more than five to eight percent between theoutput voltages and/or discharge rates of the battery strings, ifnon-common-mode AC noise above a given threshold is detected, if a fusetrips a specified number of times during a period, and/or the like. Ifpower controller detects a discharge error, it may report a defectivestring or battery to a remote monitoring location (e.g., by sending amessage via OMC interface 320 using the STATUS signal) at which theerror may be logged, a trouble ticket opened, a technician dispatched,and/or the like. Power controller may also take other actions, such asdisconnecting the defective string from the battery circuit node using astring enable signal STR_EN, updating power controller's hardwareconfiguration (e.g., to indicate that the string is defective), and/orother suitable actions.

At block 740, power controller 210 monitors the remaining parked stringsthat are unconnected to the battery circuit node. For example, powercontroller 210 may monitor the voltage, I/O current, I/O power, and/ordischarge rate of the remaining strings(s) so that power controller mayperform decision block 750 and repeat blocks 710 and 720 as necessary.

At decision block 750, power controller 210 determines whether thevoltage of the target string(s) and other connected strings is stillabove the remaining strings. If not, process 700 repeats starting atblock 710. Otherwise, process 700 proceeds to decision block 760, wherepower controller determines whether the power failure has ended, e.g.,whether a blackout has ended and primary power signal is back to itsfull power. If the power failure has ended, process 700 returns.Otherwise process 700 repeats starting at block 730.

CONCLUSION

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” As used herein, the terms “connected,”“coupled,” or any variant thereof means any connection or coupling,either direct or indirect, between two or more elements; the coupling orconnection between the elements can be physical, logical, or acombination thereof. Additionally, the words “herein,” “above,” “below,”and words of similar import, when used in this application, refer tothis application as a whole and not to any particular portions of thisapplication. Where the context permits, words in the above DetailedDescription using the singular or plural number may also include theplural or singular number respectively. The word “or,” in reference to alist of two or more items, covers all of the following interpretationsof the word: any of the items in the list, all of the items in the list,and any combination of the items in the list.

The above Detailed Description of examples of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific examples for the invention are describedabove for illustrative purposes, various equivalent modifications arepossible within the scope of the invention, as those skilled in therelevant art will recognize. For example, while processes or blocks arepresented in a given order, alternative implementations may performroutines having steps, or employ systems having blocks, in a differentorder, and some processes or blocks may be deleted, moved, added,subdivided, combined, and/or modified to provide alternative orsubcombinations. Each of these processes or blocks may be implemented ina variety of different ways. Also, while processes or blocks are attimes shown as being performed in series, these processes or blocks mayinstead be performed or implemented in parallel, or may be performed atdifferent times. Further any specific numbers noted herein are onlyexamples: alternative implementations may employ differing values orranges.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various examples described above can be combined to providefurther implementations of the invention. Some alternativeimplementations of the invention may include not only additionalelements to those implementations noted above, but also may includefewer elements.

Any patents and applications and other references noted above, includingany that may be listed in accompanying filing papers, are incorporatedherein by reference. Aspects of the invention can be modified, ifnecessary, to employ the systems, functions, and concepts of the variousreferences described above to provide yet further implementations of theinvention.

These and other changes can be made to the invention in light of theabove Detailed Description. While the above description describescertain examples of the invention, and describes the best modecontemplated, no matter how detailed the above appears in text, theinvention can be practiced in many ways. Details of the system may varyconsiderably in its specific implementation, while still beingencompassed by the invention disclosed herein. As noted above,particular terminology used when describing certain features or aspectsof the invention should not be taken to imply that the terminology isbeing redefined herein to be restricted to any specific characteristics,features, or aspects of the invention with which that terminology isassociated. In general, the terms used in the following claims shouldnot be construed to limit the invention to the specific examplesdisclosed in the specification, unless the above Detailed Descriptionsection explicitly defines such terms. Accordingly, the actual scope ofthe invention encompasses not only the disclosed examples, but also allequivalent ways of practicing or implementing the invention under theclaims.

To reduce the number of claims, certain aspects of the invention arepresented below in certain claim forms, but the applicant contemplatesthe various aspects of the invention in any number of claim forms. Forexample, while only one aspect of the invention is recited as ameans-plus-function claim under 35 U.S.C. sec. 112, sixth paragraph,other aspects may likewise be embodied as a means-plus-function claim,or in other forms, such as being embodied in a computer-readable medium.(Any claims intended to be treated under 35 U.S.C. §112, ¶6 will beginwith the words “means for”, but use of the term “for” in any othercontext is not intended to invoke treatment under 35 U.S.C. §112, ¶6.)As another example, although the current claims are primarily directedto systems and methods that provide backup or supplementary batterypower to radio and telecommunications circuitry at a cell site or basestation, the inventors recognize that the invention could be practicedin any environment where a battery circuit powers a system, includingany environment where a battery circuit provides backup or supplementarypower to a system. Accordingly, the applicant reserves the right topursue additional claims after filing this application to pursue suchadditional claim forms, in either this application or in a continuingapplication.

1. A system for providing supplementary or emergency power, the systemcomprising: a battery circuit connected to a battery circuit node,wherein the battery circuit node is configured to provide battery power,and wherein the battery circuit comprises— multiple battery strings,wherein each battery string comprises: one or more batteries coupled ina series configuration; and at least one switch circuit configured toselectively couple the one or more batteries to the battery circuitnode, wherein the battery circuit node is configured to provide power,and to receive a charging current for charging batteries; and a powercontroller configured to: selectively couple one or more of the multiplebattery strings in the battery circuit to the battery circuit node,wherein a battery string coupled to the battery circuit node operates asan active battery string, wherein the active battery string provides viathe battery circuit node, and wherein the active battery string activelyreceives the charging current to maintain the active battery string ator near a full charge; selectively decouple at least one of the one ormore of the multiple battery strings in the battery circuit from thebattery circuit node, wherein a battery string decoupled from thebattery circuit node operates as a parked battery string, wherein theparked battery string does not actively receive the charging current;and, upon an occurrence of a battery change event, to— (i) couple theparked battery string to the battery circuit node to provide power andto actively receive the charging current; or (ii) decouple the activebattery string from the battery circuit node and to no longer receivethe charging current; or (iii) both (i) and (ii); and, wherein thebattery change event includes at least one of a specified chargingevent, a specified testing event, or a power failure event.
 2. Thesystem of claim 1, further comprising: a rectifier and switch circuitconfigured to charge the battery circuit and to route power from thebattery circuit to a load under control of the power controller.
 3. Thesystem of claim 1, wherein each battery string further includes anassociated current sensor, and wherein the power controller is furtherconfigured to monitor each of the current sensors to determine a statusof an associated battery string.
 4. The system of claim 1, wherein thesystem is configured to test the battery circuit, charge the batterycircuit, and provide power to radio and telecommunications circuitry tohandle power failures.
 5. The system of claim 1, wherein the powercontroller is further configured to select one or more of the multiplebattery strings in the battery circuit to operate as active batterystrings on the basis of: a function of time; a measured capacity of oneor more battery strings; a calculated capacity of one or more batterystrings; or an expected capacity of one or more battery strings.
 6. Amethod, comprising: determining an indication that one or moreoperations related to management of a battery circuit is to beperformed, wherein the battery circuit comprises multiple batterystrings, and wherein each battery string in the battery circuit furthercomprises: two or more batteries arranged in a serial fashion andconfigured to provide backup power; a string connection switchconfigured to selectively couple and decouple the battery string from abattery circuit node; and, a sensor configured to provide a string sensesignal indicating conditions relating to at least one state of thebattery string; and wherein the determined indication comprises: abattery test event indicating that the battery circuit is to be tested;a battery rotation event indicating that at least one of the followingis to be performed— (i) rotating one or more battery strings from aparked status into an active status, (ii) rotating one or more batterystrings from an active status to a parked status, or (iii) both (i) and(ii); initiating a battery test process when the determined indicationcomprises the battery test event, wherein the battery test processcomprises selectively coupling one or more battery strings to thebattery circuit node for testing; initiating a battery rotation processwhen the determined indication comprises the battery rotation event,wherein the battery rotation process comprises at least one or both of—selectively coupling one or more battery strings to the battery circuitnode and into the active status, and selectively decoupling one or morebattery strings from the battery circuit node and into the parkedstatus.
 7. The method of claim 6, wherein the determined indicationfurther comprises: a battery charging event indicating that the batterycircuit is to be charged; and a power failure event indicating that anexternal power failure exists; and wherein the method further comprises—initiating a battery charging process when the determined indicationcomprises the battery charging event, wherein the battery chargingprocess comprises selectively coupling one or more battery strings tothe battery circuit node for charging; and, initiating a power failurehandling process when the determined indication comprises the powerfailure event, wherein the power failure handling process comprisesselectively coupling one or more battery strings in the parked status tothe battery circuit node to provide backup power to the radio andtelecommunications circuitry at the base station.
 8. The method of claim6, wherein a battery test process and a battery charging process aresubstantially simultaneously performed, and wherein the method furthercomprises: selecting a target battery string; adjusting a voltageapplied to the battery circuit node to equalize a voltage across one ormore active battery strings coupled to the battery circuit node and avoltage across the target battery string, wherein the voltage applied isselected based on at least one of the following: the voltage across thetarget battery string, the voltage across one or more active batterystrings, environmental conditions near the battery circuit, or types ofbatteries in the battery circuit; selectively coupling the targetbattery string to the battery circuit node when the voltage across theone or more active battery strings approximately reaches the voltageacross the target battery string; applying a charging voltage to thebattery circuit node, wherein the charging voltage is based on a type ofbattery in the battery circuit or environmental conditions at or nearthe battery circuit; and utilizing the string sense signal associatedwith the target battery string to determine whether the target batterystring experiences anomalous currents in response to the appliedcharging voltage.
 9. The method of claim 6, wherein the determinedindication comprises a battery charging event, and the detected batterycharging event comprises a voltage of a battery string in the batterycircuit falling below a threshold value, wherein the threshold valuecorresponds to a particular level of estimated charge stored in thebattery string.
 10. The method of claim 6, wherein the determinedindication comprises the battery charging event, and the detectedbattery charging event comprises: a current time occurring within anoff-peak time period when commercial utility power rates are lower thanrates for other periods; and a voltage of a battery string in thebattery circuit falling below a threshold value, wherein the thresholdvalue corresponds to a selected level of estimated charge stored in thebattery string.
 11. The method of claim 6, wherein selectively couplinga battery string to the battery circuit node comprises: adjusting avoltage across one or more other battery strings coupled to the batterycircuit node to approximately equal a voltage across the battery stringto be selectively coupled; and utilizing a string connection switch toselectively couple the battery string to the battery circuit node whenthe voltage across the one or more other battery strings approximatelyequals the voltage across the battery string that is to be selectivelycoupled.
 12. The method of claim 6, wherein initiating a battery testprocess further comprises: selecting a target battery string;selectively coupling the target battery string to the battery circuitnode; and utilizing the string sense signal associated with the targetbattery string to determine whether the target battery stringexperiences anomalous currents in response to a charging source appliedto the battery circuit node, and comparing currents in the targetbattery string to currents in other battery strings in the batterycircuit.
 13. The method of claim 6, wherein initiating a battery testprocess further comprises selecting a target battery string, selectivelycoupling the target battery string to the battery circuit node, andutilizing the string sense signal associated with the target batterystring to determine whether the target battery string has asubstantially different charging, discharging, or self-discharging rateas compared to one or more other battery strings in the battery circuit.14. The method of claim 6, wherein initiating a battery test processfurther comprises selecting a target battery string via anelectronically resettable breaker positioned in serial with the one ormore batteries of the target battery string, selectively coupling thetarget battery string to the battery circuit node, and utilizing theelectronically resettable breaker to determine whether the targetbattery string has failed.
 15. The method of claim 6, wherein thedetermined indication comprises a battery test event, and the detectedbattery test event comprises a voltage of a battery string in thebattery circuit falling below a threshold value, wherein the thresholdvalue corresponds to a particular level of estimated charge stored inthe battery string.
 16. The method of claim 6, wherein initiating abattery rotation process further comprises selecting a battery string torotate into an active status, wherein the battery string is selected bydetermining which battery string in the battery circuit has a lowestaccumulated time in active status.
 17. A non-transitorycomputer-readable medium carrying instructions that, when performed by aprocessor, perform a method for a battery circuit, the methodcomprising: determining an indication that at least one of multiplebattery strings is to be charged and tested, wherein each battery stringin the battery circuit further comprises: multiple batteries arranged ina serial fashion; a connection switch configured to selectively coupleand decouple the battery string; and a sensor configured to provide astring sense signal indicating conditions relating to a state of thebattery string; and, initiating battery test and charging processes,further comprising: selecting a target battery string having a voltage;adjusting a voltage applied so that a voltage across one or more activebattery strings reaches the voltage across the target battery string,wherein the voltage applied is selected based on at least one of thefollowing: the voltage across the target battery string, the voltageacross one or more active battery strings, one or more environmentalconditions at or near the battery circuit, or a type of at least onebattery in the battery circuit; selectively coupling the target batterystring to supply power, as needed, to radio and telecommunicationscircuitry at the base station when the voltage across the one or moreactive battery strings approximately reaches the voltage across thetarget battery string; and, utilizing the string sense signal associatedwith the target battery string to determine whether the target batterystring experiences anomalous currents in response to the appliedcharging voltage.
 18. The non-transitory computer-readable medium ofclaim 17, wherein a current sensor is coupled to and associated witheach battery string; and the method further comprising: monitoring eachof the current sensors to determine a status of an associated batterystring; monitoring a particular current sensor associated with aparticular battery string to determine a self-discharging rate of theparticular battery string; and evaluating whether the determinedself-discharging rate is anomalous as compared to other battery stringsin the battery circuit or based on empirical data.
 19. Thenon-transitory computer-readable medium of claim 17, wherein a currentsensor is coupled to and associated with each battery string; and themethod further comprising: monitoring each of the current sensors todetermine a status of an associated battery string; monitoring aparticular current sensor associated with a particular battery string todetermine a charging or discharging rate of the particular batterystring; and evaluating whether the determined charging or dischargingrate is anomalous as compared to other battery strings in the batterycircuit or based on empirical data.
 20. The non-transitorycomputer-readable medium of claim 17, further comprising: beginningcharging the battery circuit at a first voltage that is based on avoltage across a parked battery string having a lowest string voltage ascompared to other parked battery strings, applying a second, highercharging voltage to the battery circuit, and repeatedly coupling anadditional battery string to the battery circuit as a voltage of thecoupled battery strings rises to a voltage of the additional batterystring due to the second, applied charging voltage.